Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$225.82	11.528%	$251.8525	$251.85	$251.85	$251.90
Purchase #2	$90.53	4.430%	$94.5405	$94.54	$94.55	$94.50
Purchase #3	$49.31	10.162%	$54.3209	$54.32	$54.30	$54.30
Purchase #4	$147.32	10.570%	$162.8917	$162.89	$162.90	$162.90
Purchase #5	$133.38	8.763%	$145.0681	$145.07	$145.05	$145.10
Purchase #6	$76.67	12.790%	$86.4761	$86.48	$86.50	$86.50
Purchase #7	$189.63	5.149%	$199.394	$199.39	$199.40	$199.40
7 purchase totals =	$912.66		$994.5438	$994.54	$994.55	$994.60